Examkin

Question

Difficulty: HardLatitude, Longitude, and Time Calculations

Town X is located at longitude 15∘W15^\circ\text{W} where the local solar time is recorded as 08:20 AM08:20\text{ AM}. At the exact same instant, a solar observatory at Town Y records a local solar time of 05:00 PM05:00\text{ PM}. What is the longitude of Town Y?

  1. 115∘E115^\circ\text{E}Answer
  2. B
    115∘W115^\circ\text{W}
  3. C
    145∘E145^\circ\text{E}
  4. D
    145∘W145^\circ\text{W}

Answer

The longitude of Town Y is 115∘E115^\circ\text{E}.
Because Town Y has a local solar time of 05:00 PM05:00\text{ PM} compared to 08:20 AM08:20\text{ AM} at Town X, Town Y is 8 hours 40 minutes8\text{ hours } 40\text{ minutes} ahead. Converting this time difference to angular distance (520 minutes÷4=130∘520\text{ minutes} \div 4 = 130^\circ) shows Town Y is 130∘130^\circ east of 15∘W15^\circ\text{W}. Traveling 15∘15^\circ east reaches the Greenwich Meridian (0∘0^\circ), and the remaining 115∘115^\circ east places Town Y at 115∘E115^\circ\text{E}.

Step-by-Step Solution

1
Calculate the time difference between Town X and Town Y
Time difference = 05:00 PM(17:00)−08:20 AM=8 hours 40 minutes05:00\text{ PM} (17:00) - 08:20\text{ AM} = 8\text{ hours } 40\text{ minutes}
Determining the time span between the two locations provides the basis for calculating angular separation.
2
Convert the time difference into degrees of longitude
8 hours 40 minutes=520 minutes8\text{ hours } 40\text{ minutes} = 520\text{ minutes}. Total angular distance = 520 minutes÷4 minutes/degree=130∘520\text{ minutes} \div 4\text{ minutes/degree} = 130^\circ
Earth rotates 1∘1^\circ every 4 minutes (15∘15^\circ per hour).
3
Determine direction and final longitude of Town Y
Since Town Y's time (05:00 PM05:00\text{ PM}) is ahead of Town X's time (08:20 AM08:20\text{ AM}), Town Y lies to the East of Town X. Moving 130∘130^\circ East from 15∘W15^\circ\text{W}: 130∘−15∘=115∘E130^\circ - 15^\circ = 115^\circ\text{E}
Locations further east experience later local solar times. Crossing the 0∘0^\circ Prime Meridian shifts coordinates from West to East.

Key Concept

Calculating Longitude from Local Solar Time Differences Across Hemispheres
Rate this question

Topics

Latitude, Longitude, and Time Calculations

More questions from this topic